Diagnostic Aids

Perform this test only when directed by QUICK TEST. This test is intended to diagnose the following:

Wiring Harness Circuits (CHT, SIG RTN & VREF)
Faulty CHT Sensor
Faulty Powertrain Control Module (PCM)

1) DTC P1116 Or P1288: Check CHT Sensor Operaton

DTC P1116 or P1228 indicates CHT sensor is out of self-test range. Possible causes for these faults are:
- Engine Overheating
- Low Coolant Level
- Faulty Sensor
- Faulty Sensor Connector
- Poor Thermostat Operation
Start engine and raise speed to 2000 RPM until engine is at normal operating temperature. If engine is a no-start or has a stalling problem, go to step 3). Perform KOER ON-DEMAND SELF-TEST . Check for DTC P1116 or P1288. If DTC P1116 or P1288 is not present, engine temperature was not stabilized. Service any other DTCs and repeat QUICK TEST . If DTC P1116 or P1288 is present, go to next step.

2) Check VREF Circuit Voltage At TP Sensor

Turn ignition switch to OFF position. Disconnect TP sensor connector. Turn ignition switch to ON position. Using a DVOM, measure voltage between TP sensor harness connector VREF and SIG RTN terminals. See Figure or Figure . If voltage is 4-6 volts, VREF voltage is okay. Reconnect TP sensor and go to next step. If voltage is not 4-6 volts, go to TEST C, step 1).

3) Check CHT Sensor Circuit Resistance

Turn ignition switch to OFF position. Disconnect CHT sensor 2-pin connector. Using a DVOM, measure resistance between CHT sensor terminals. See CHT SENSOR SPECIFICATIONS table. If resistance is not as specified, replace CHT sensor. If resistance is as specified and engine is a no-start or engine has a stalling concen, see SYMPTOMS in TROUBLE SHOOTING - NO CODES article. If resistance is as specified, engine starts or has a stalling concen, go to next step.

CHT SENSOR SPECIFICATIONS ⁽¹⁾

Temperature °F (°C)

Volts

Ohms

-40 (-40)

4.89

965,808

-22 (-30)

4.81

513,019

-4 (-20)

4.67

283,664

14 (-10)

4.45

162,584

32 (0)

4.14

96,255

50 (10)

3.73

59,175

68 (20)

3.26

37,387

86 (30)

2.74

24,215

104 (40)

2.23

16,043

122 (50)

1.76

10,850

140 (60)

1.36

7487

158 (70)

1.04

5268

176 (80) ⁽²⁾

.79 Or 3.99

3775

185 (85) ⁽²⁾

.69 Or 3.86

3215

194 (90) ⁽²⁾

.60 Or 3.71

2750

203 (95) ⁽²⁾

.53 Or 3.56

2361

212 (100) ⁽²⁾

.46 Or 3.41

2034

248 (120)

2.74

1155

284 (140)

2.10

689

302 (150)

1.81

542

320 (160)

1.55

430

338 (170)

1.33

345

356 (180)

1.13

279

374 (190)

.96

228

392 (200)

.82

188

410 (210)

.70

155

428 (220)

.60

130

446 (230)

.51

109

464 (240)

.44

482 (250)

.35

500 (260)

.33

⁽¹⁾	Value may vary by 15 percent.

⁽²⁾	At this temperature, there is a voltage overlap zone due to a dual switching resistor circuit on CHT input. It is possible to have either a cold end (low voltage) or hot end (high voltage) measurement at the same temperature. Either voltage specification listed is correct.

4) Check CHT Sensor Resistance With Engine Running

Start engine. Ensure engine is at normal operating temperature. Raise engine speed to 2000 RPM for 2 minutes. Using a DVOM, measure resistance between CHT sensor terminals. See CHT SENSOR SPECIFICATIONS table. If resistance is as specified, replace PCM. If resistance is not as specified, replace CHT sensor.

5) KOEO & KOER DTC P1289 Or P1290: Check CHT V PID Voltage

These DTCs indicate CHT sensor circuit is shorted or open. Possible causes for these faults are:
- Open Or Grounded CHT Circuit
- Faulty Sensor
- Faulty Sensor Connector
- Faulty Powertrain Control Module (PCM)
Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, select CHT V PID from PID/DATA MONITOR & RECORD menu. If CHT V PID voltage is less than .2 volt, go to next step. If CHT V PID voltage is .2 volt or more, go to step 7).

6) Check For Grounded Circuit

Disconnect CHT sensor 2-pin connector. Using scan tool, select CHT V PID from PID/DATA MONITOR & RECORD menu. If CHT V PID voltage is more than 4.6 volts, replace CHT sensor. If CHT V PID voltage is 4.6 volts or less, go to step 21).

7) Check For Open Circuit

Connect a jumper wire between CHT sensor harness connector terminals. Turn ignition switch to ON position. Using scan tool, select CHT V PID from PID/DATA MONITOR & RECORD menu.
NOTE: If communication link error is displayed, remove jumper wire and go to step 12).

If CHT V PID voltage is less than .2 volt, replace CHT sensor. If PID voltage is .2 volt or more, remove jumper wire and go to step 11).

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 7) to step 10). No test procedures have been omitted.

10) KOEO & KOER DTC P0118: Simulate Opposite CHT Signal To PCM

This DTC indicates CHP sensor signal is more than self-test maximum. Possible causes for this fault are:
- Open Circuit
- Sensor Signal Shorted To Power
- Faulty CHT Sensor Or Connector
- Faulty PCM
Turn ignition switch to OFF position. Disconnect CHT sensor 2-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Connect a jumper wire between CHT sensor harness connector terminals. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position.

NOTE: If communication link error is displayed, remove jumper wire and go to step 12).

Using scan tool, select CHT V PID from PID/DATA MONITOR & RECORD menu. If CHT V PID voltage is less than .2 volt, replace CHT sensor. If CHT V PID voltage is .2 volt or more, remove jumper wire and go to next step.

11) Check CHT Signal & SIG RTN Circuits For Opens

Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance of CHT circuit between PCM harness connector terminal and CHT sensor harness connector terminal. See Fig 1 or Fig 2 . Using a DVOM, measure resistance of SIG RTN circuit between PCM harness connector terminal and CHT sensor harness connector terminal. If both resistance measurements are less than 5 ohms, replace PCM. If either resistance measurement is 5 ohms or more, repair open in affected circuit.

Fig 1: Identifying CHT Sensor Harness Connector Terminals (Except Tribute)
Courtesy of FORD MOTOR CO.

Fig 2: Identifying CHT Sensor Harness Connector Terminals (Tribute)
Courtesy of FORD MOTOR CO.

12) Check CHT Signal Circuit For Short To VREF

Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance between PCM harness connector CHT and VREF terminals. See WIRING DIAGRAMS article. See Figure. If resistance is more than 10 k/ohms, replace PCM. If resistance is 10 k/ohms or less, locate and repair short circuit to VREF.
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 12) to step 20). No test procedures have been omitted.

20) KOEO & KOER DTC P0117: Simulate Opposite Signal To PCM

DTC P0117 indicates CHT sensor signal is less than self-test minimum. Minimum signal for CHT sensor is .2 volt. Possible causes for this fault are:
- Open Or Grounded Circuit
- Faulty CHT Sensor
- Faulty PCM
Turn ignition switch to OFF position. Disconnect CHT sensor 2-pin connector. Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, select CHT V PID from PID/DATA MONITOR & RECORD menu. If CHT V PID voltage is more than 4.6 volts, replace CHT sensor. If CHT V PID voltage is 4.6 volts or less, go to next step.

21) Check VREF Circuit Voltage At TP Sensor

Disconnect TP sensor connector. Using a DVOM, measure voltage between TP sensor harness connector VREF and SIG RTN terminals. See Figure. If voltage is 4-6 volts, VREF voltage is okay. Reconnect TP sensor and go to next step. If voltage is not 4-6 volts, go to TEST C, step 1).

22) Check CHT Signal Circuit For Short To Ground

Turn ignition switch to OFF position. Disconnect PCM connector(s). Inspect connector for loose, damaged or corroded terminals. Repair as necessary. Using a DVOM, measure resistance between PCM harness connector CHT terminal, and PWR GND and SIG RTN terminals. See PCM PWR GND, SIG RTN & VREF TERMINAL IDENTIFICATION table. See Figure, Fig 1 or Fig 2 . If all resistance measurements are more than 10 k/ohms, replace PCM. If any resistance measurement is 10 k/ohms or less, repair short in affected circuit.
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 22) to step 30). No test procedures have been omitted.

30) DTC P1285: Early Warning Of Engine Overheat Condition

This DTC indicates that PCM has sensed an engine overheat condition from CHT sensor. Check cooling system for leaks and restrictions. Check coolant level and cooling fan operation. Check for cause of overheat condition. Repair as necessary. If cooling system is okay and no faults are found, go to step 3).
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 30) to step 40). No test procedures have been omitted.

40) Engine Temperature Warning Light Always On Or Temp Gauge Reads Hot, Engine Is Not Overheating

If QUICK TEST was performed and no DTCs are present, go to next step. If QUICK TEST was not performed, perform QUICK TEST and service any DTCs that are present.

41) Engine Temperature Warning Light Always On Or Temp Gauge Reads Hot (No DTCs)

This DTC indicates that PCM has sensed an engine warning light circuit fault. Possible causes for this fault are:
- Faulty Engine Coolant Temperature (ECT) Sensor
- Faulty Instrument Cluster
- Faulty Wiring Harness Between PCM & Instrument Cluster
- Faulty PCM
Disconnect PCM connector(s). Turn ignition switch to ON position. If engine temperature warning light is off, or temperature gauge measurement is in the normal zone, replace PCM. If engine temperature warning light is still on, or temperature gauge measurement is in the "H" (Hot) zone, check instrument cluster and temperature warning light circuits. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT for diagnosis and testing.

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 41) to step 80). No test procedures have been omitted.

80) Continuous Memory DTC P0116: Check CHT Sensor Resistance With Engine Off

DTC P0116 indicates CHT sensor drifted higher than normal sensor calibration curve and could prevent one or more OBD-II monitors from functioning. PCM will set DTC P0116 when all of the following conditions are met:
- Cylinder head temperature at engine start up exceeds IAT temperature by more than calibrated value, about 30°F (1°C).
- Cylinder head temperature exceeds a calibrated value, about 225°F (107°C).
- Fuel, HEGO, catalyst and misfire monitors have not completed.
- Calibrated timer to set DTC P0116 has expired.
Possible causes for this fault are:
- Faulty CHT Sensor
- Coolant System Fault
Ensure engine temperature is at ambient room temperature. A soak period of 6 hours may be required. Disconnect CHT sensor 2-pin connector. Turn ignition switch to ON position. Using a DVOM, measure resistance between CHT sensor terminals. See CHT SENSOR SPECIFICATIONS table. If resistance is as specified, go to next step. If resistance is not as specified, replace CHT sensor.

81) DTC P0116: Check CHT Sensor Resistance With Engine Running

Start engine and bring to operating temperature. Run at 2000 RPM for 2 minutes. Using a DVOM, measure resistance between CHT sensor terminals. See CHT SENSOR SPECIFICATIONS table. If resistance is not as specified, replace CHT sensor. If resistance is as specified, fault is not present at this time. Perform DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS. Ensure OBD-II DRIVE CYCLE PROCEDURES are performed to ensure monitors can be activated.
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 81) to step 90). No test procedures have been omitted.

90) Continuous Memory DTC P0117, P0118, P1117, P1289 Or P1290: Intermittent Check

These DTCs indicate intermittent CHT sensor failure. Possible causes for these faults are:
- Open Or Grounded Circuit
- Faulty CHT Sensor
- Low Coolant Level
- Faulty PCM
Connect scan tool to Data Link Connector (DLC). Turn ignition switch to ON position. Using scan tool, select CHT PID from PID/DATA MONITOR & RECORD menu. While observing CHT PID, lightly tap on CHT sensor and wiggle sensor connector to simulate road shock. A fault is indicated by a sudden change of CHT PID temperature reading. If no fault is indicated, go to next step. If fault is indicated, turn ignition switch to OFF position. Disconnect and inspect connectors. If connectors are okay, replace CHT sensor. Clear DTCs and perform DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS. Ensure OBD-II DRIVE CYCLE PROCEDURES are performed to verify repair. Repeat QUICK TEST .

91) Check Wiring Harness

Ensure CHT PID is still selected. Starting at CHT sensor connector and working toward PCM, wiggle, shake and bend small sections of wiring harness. A fault is indicated by a sudden change of CHT PID temperature reading. If no fault is indicated, go to next step. If fault is indicated, isolate and repair as necessary. Clear DTCs and perform DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS. Ensure OBD-II DRIVE CYCLE PROCEDURES are performed to verify repair. Repeat QUICK TEST .

92) Check PCM Wiring Harness

Turn ignition switch to OFF position. Disconnect CHT sensor and PCM harness connectors. Inspect connectors for loose, damaged or corroded terminals. Repair as necessary. Clear DTCs and perform DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS. Ensure OBD-II DRIVE CYCLE PROCEDURES are performed to verify repair. Repeat QUICK TEST . If connectors are okay, problem cannot be located at this time. Clear DTCs and perform DRIVE CYCLE PROCEDURES under ADDITIONAL SYSTEM FUNCTIONS. Ensure OBD-II DRIVE CYCLE PROCEDURES are performed to verify repair. Repeat QUICK TEST .
NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 92) to step 100). No test procedures have been omitted.

100) DTC P0217 Or P1299: Engine Overheat Condition Occurred

This DTC indicates an engine overheat condition was detected by CHT sensor and fail-safe cooling strategy was activated. Possible causes for this fault are:
- Cooling System Fault
- Low Coolant Level
- Engine Mechanical Fault
Locate cooling system fault and repair as necessary.